Nonwoven wick unit

ABSTRACT

A nonwoven wick unit having selectively controlled liquid transfer and reservoir capacity is obtained by limiting the distance between the individual filaments of a filamentary tow, for example, by needle punching the tow. The liquid transfer properties of the unit can be further enhanced by surface treatment such as cutting the surface fibers and brushing up the cut ends.

3 United States Patent Kamp et al.

[ Mar. 14, 1972 [54] NONWOVEN WICK UNIT [72] Inventors: Ewald A. Kamp, Chicago; Emmett J. Massey, Homewood, both of Ill.

[73] Assignee: Union Carbide Corporation, New York,

[22] Filed: Oct. 15, 1969 [21 Appl. No.: 866,748

[52] US. Cl ..184/64, 28/722, 252/4255, 308/87, 401/199 [51] Int. Cl ..F16n 7/12 [58] Field of Search ..252/425.5; 184/3, 64; 28/722; 308/87; 401/196, 198, 199

[56] References Cited UNITED STATES PATENTS 3,111,702 11/1963 Berger ..401/198X Primary Examiner-Manuel A. Antonakas AttorneyPaul A. Rose, J. Hart Evans and Michael A. Caputo [57] ABSTRACT A nonwoven wick unit having selectively controlled liquid transfer and reservoir capacity is obtained by limiting the distance between the individual filaments of a filamentary tow, for example, by needle punching the tow. The liquid transfer properties of the unit can be further enhanced by surface treatment such as cutting the surface fibers and brushing up the cut ends.

14 Claims, No Drawings NONWOVEN wrcrr UNIT This invention relates to nonwoven wick units and more particularly to nonwoven wick units which are particularly well suited for use as railroad journal box lubricators.

The art of wicking liquids to provide a self-acting transport means from a reservoir to a point of use is old and probably had its discovery in prehistoric times, e.g., wicks used as fuel feed for lamps. The advent of the machinery age applied the principle of the wick feed lubricant to bearings. One of the more extensive, if less popularly known, uses of wicks has been in railroad freight cars which have been substantially unchanged in 50 years. The standard design called for cotton waste stuffed into the journal box. As car speed and weight increased, and hot boxes became more frequent, a-more reliable means of providing such wicking oil supply was achieved through the use of a high density neoprene sponge pad enclosed in a cotton chenille bag. The particular requirements in journal bearings, which include vibration, shock, and a relatively primitive lubricant retainer with infrequent servicing, make it mandatory that the wick also have ample reservoir capacity. In the presently used lubricators, the cotton chenille provides the liquid transport, and the neoprene sponge the reservoir and spring element. As a reservoir, the neoprene is relatively inefficient and, in actual use, is subject to high abrasive and chemical deterioration.

Experience and visual observation have taught that a twisted thread or rope, whether used singly or in a woven fabric, acts as an efficient wick. However, efficient wicks woven from threads or yarns appeared to lack the ability to retain sufficient quantities of oil to satisfy railroad requirements.

It is an object of the present invention to provide an improved wicking device having both adequate liquid transport and reservoir capacity.

It is a further object of the invention to provide a nonwoven wick permitting predetermined control of wicking height and absorptive capacity.

It is a further object to provide a wick which, in combination with a pressure producing pad, can be used as an improved railroad bearing lubricator or similar device.

These and other objects are achieved by a nonwoven wick unit formed from a filamentary tow having a plurality of its filaments restrained to limit the distance between filaments and selectively control liquid transport and reservoir capacity. As will be described in greater detail hereinafter, the desirable properties of the restrained filament wick unit of the present invention can be further improved by supplementary surface treating, e.g., cutting the surface fibers and brushing up the ends.

The term tow as used herein, refers to a large number of continuous, substantially parallel, filaments without definite twist collected in the form of a loose strand. Generally speaking the term tow is considered applicable if the total denier of such strand exceeds 15,000, but it could exceed 5x10 The number of filaments in a tow is calculated by dividing the total denier of the tow by the denier per filament.

While the theory of the present invention is incomplete at present, and applicant does not desire to be bound by any theory of invention, the mechanism of this invention can be explained by the well-known general equation for the capillary constant a =rh=2ylgd wherein a is the capillary constant in millimeters, r is the radius of curvature of the inner tube surface, h is the height to which a liquid will rise, y is the surface tension of the liquid, and d is the density of the liquid.

Since in an actual lubricator, lift heights of 100-200 millimeters are mandatory, it was theorized that compactly bundled continuous filament strands might yield improved results. When a cross section of a fibrous bundle is considered, it becomes probable that the inside radius r is analogous to the corner fillet between two adjacent filaments and, therefore, is modified proportionately by the distance between fibers. A new relation to express this property could be written wherein r is the outside curvature of the fiber, k is a conversion factor, and zeta (L) is the distance between the fibers. For a given r, k would be a function of the geometry of the system and the height to which the liquid will rise (h) is a function of k, and is nonlinear. This conversion factor determines the distance zeta as h increases and can therefore be termed a swelling factor". In the absence of a complete valid theory which defines h, k will have to be derived empirically.

The rise of the liquid to height h produces a hydraulic pressure which in turn generates swelling" of the filament bundles. This swelling, if unrestrained, would rapidly limit I: by increasing zeta. lt is therefore desirable to apply restraints to the structure. The purpose of these restraints, as taught by the basic relations, is to permit a desirable balance of wicking height and swelling or volumetric absorption. Such restraints can be provided by sewing the structure together with an elastic stitch or tying it together with an elastic filament. 1n the preferred embodiment such control can be provided by needle punching or looming filament bundles together.

The process of needling fibers into filament batts iswell known in the art and, for this reason, will not be described in great detail. However, in the framework of the preseiit-invention, the needling is performed on fiber batts with a majority of the filaments, preferably about percent, arranged parallel to the machine direction. By selectively controlling the conditions of fiber interlock, swelling of the sheet can be controlled and thereby the required balance of capillary 'wicking" height and volumetric absorption or reservoir capacity of the material can be controlled.

The type and gauge of needle used, as well as the number of needles in the board, the machine speed and the material advance can all play separate roles in controlling the balance between wicking height and absorption. It has been found that good interlock of parallel tow fibers is obtained within the range of to 5,000 perforations per square inch. Above this range the absorption is limited and fiber breakup reduces capillary action.

To obtain optimum vertical fluid lift at least about 50 percent of the fibers should remain substantially in their original alignment axis with a gross deviation of not more than 15 to 20 and should have a substantial residual unbroken length after needling of not less than about 4 inches. These optimum conditions were found to be valid on tow bundles in the range of about 75,000 to 240,000 total denier.

The thickness or denier of the individual fibers also plays an important role. From the relation expressed above, it can be seen that a small fiber radius will produce a greater lift height, and therefore the finer the denier the greater the lift potential. However, there are practical limits in fiber processing and it has been found that a range of 3 to 6 denier is most effective for wicking purposes. Above 6 denier the lift height is reduced while below 3 denier the fibers are weak and are easily broken during processing.

Since the liquid transport of the wick unit of the present invention operates through a capillary mechanism, and capillary flow is dependent primarily upon the geometry and surface tension of the particular fibers, it is possible to select material properties best suited to a specific liquid application using the vast inventory of old as well as new fibers. It is therefore possible to design devices to withstand the effects of solvents, acids, alkali, temperature, etc. without having to undergo the extensive process development inherent in presently used wicking devices, e.g., foamed products. Fibers such as glass or other siliceous materials, nylons, polyester, olefins and cellulosics can find their proper place where required with no appreciable change in the manufacturing process of this invention.

The high filament strength of 50,000 to 100,000 p.s.i. available in synthetic fibers and 200,000 to 300,000 p.s.i. in siliceous fibers permits tailoring the product to applications requiring either strength or vibration resistance or the ability to withstand abrasion. Moreover, because of the selective design features and the ability to absorb liquid up to percent of the fiber volume occupied, devices according to the present invention will be light in weight, compact and inexpensive, or conversely, can be given larger capacities than any other material having comparable properties, such as foamed rubber.

Preferred fibers for use in the wicks of the present invention are the so-called manmade fibers which include the acetates, triacetates, acrylics, modacrylics, polyamides, olefins, polyesters, rayons, urethanes, vinyls, vinylidenes, fluorocarbons, rubbers and inorganics.

As used herein, acetates are those fibers in which the fiber forming substance is cellulose acetate. Where not less than 92 percent of the hyroxyl groups are acetylated, the term triacetate is applied.

Acrylics are those fibers in which the fiber-forming substance is any long chain synthetic polymer composed of at least 85 per cent by weight of acrylonitrile units having the formula l CN.

Modacrylics are those fibers composed of less than 85 percent but at least 35 percent by weight of acrylonitrile units. An example of such a fiber is Dynel.

Polyamides are those fibers, such as the nylon, having recurring amide groups as an integral part of the polymer chain.

Olefins are those fibers, such as polypropylene, which are composed of any long chain synthetic polymer which is at least 85 percent by weight of ethylene, propylene, or other olefin units.

Polyesters are those fibers composed of at least 85 percent by weight of an ester of a dihydric alcohol and terephthalic acid.

Rayons are those fibers composed of regenerated cellulose as well as manufactured fibers composed of regenerated cellulose in which substituents have replaced not more than 15 percent of the hydrogens of the hydroxyl groups. Examples of commonly used rayons are viscose rayon and cuprammonium rayon.

Urethanes are those fibers in which the fiber-forming substance is a long chain synthetic polymer comprised of at least 85 percent by weight of a segmented polyurethane. These fibers are commonly referred to as spandex fibers.

The term vinyl as used herein refers to those fibers composed of at least 85 percent by weight of vinyl chloride units or those composed of at least 50 percent by weight of vinyl alcohol units in which the total of the vinyl alcohol units and any one or more of the various acetal units is at least 85 per cent by weight of the fiber.

Vinylidenes are those fibers in which the fiberforrning substance is any long chain synthetic polymer composed of at least 80 percent by weight of vinylidene chloride units. These fibers are commonly referred to as saran" fibers. Fluorocarbons are fibers composed of a polymer of a fluorocarbon resin such as tetrafluoroethylene.

A rubber fiber is one which is composed of a natural or synthetic rubber including hydrocarbons, such as natural rubber, polyiosprene, polybutadiene, copolymers of dienes and hydrocarbons, or amorphous polyolefins; copolymers of acrylonitrile and a diene composed of not more than 50 percent but at least percent by weight of acrylonitrile units; and polychloroprene or a copolymer of chloroprene in which at least 35 percent by weight of the fiber-forming substance is composed of chloroprene units.

The inorganic fibers are those which are formed from glass or metal including plastic-coated metal and metal-coated plastic.

In addition to the manmade fibers, natural fibers which are capable of being formed into a tow having long fibers, e.g., silk, are also useful in the wicks of the present invention.

Of the manmade fibers, Dynel and viscose rayon are particularly preferred for use in wicking oils.

Dynel is a copolymer of 60 weight percent vinyl chloride and 40 weight percent acrylonitrile and is manufactured and sold by Union Carbide Corporation, New York, N.Y. Dynel possesses extremely good weathering characteristics, chemical resistance, and moisture resistance and is therefore particularly well suited for applications where is is subjected to low temperature extremes, weather and infrequent servicing. Viscose rayon has better high temperature characteristics and is preferred where high temperature operation is mandatory.

The following examples are merely illustrative of the present invention and are not intended, in any manner, to be construed as limiting the scope thereof:

EXAMPLE 1 Four 1.25 X 9 X 0.25 inch samples of Dynel tow were needled with 36 gauge, 9 barb needles on a machine having a density of 96 needles per inch of width of board and a 0.25 inch advance. The total number of perforations were about 500 per square inch. Samples 1 and 4 were 6 denier fiber while samples 2 and 3 were 3 denier fiber. Sample 3 differed from Sample 2 in that it was heat shrunk to increase fiber density, while sample 4 differed from sample I in that it was formed from cut staple of 1.5-2 inch length, isotropically arranged, but otherwise processed identically. The liquid rise and liquid absorption of these samples was tested using a lubrication oil standardized by the Association of American Railroads as M906. The results of this test are set forth in Table I.

TABLE I Liquid Rise versus Liquid Absorption The results set forth in Table I indicate that interrupted randomized fibers (sample 4) had a direct adverse effect on liquid rise while a reduction of denier on continuous filaments (sample 2 versus sample 1) showed improved overall performance and a denser structure (sample 3) improved liquid rise at the expense of a loss in volumetric performance.

A correlating series of tests using twisted filamentary yarns (820 twists per linear inch) also demonstrated that improved liquid rise can be obtained by both a denser structure and reduced filament diameter. However, the twist in the filaments inhibited swelling and liquid absorption capacity.

EXAMPLE 2 The liquid transfer rate of three strips of viscose rayon fiber batt was tested. Each sample had a majority of its fibers arranged parallel to the machine direction, and was needled in the manner described in detail in Example 1. Sample 5 was pierced by 19 gauge, 9 barb needles to a depth of seveneighths inch. The needles were spaced 0.5 inch from each other in each direction. Sample 6 was surface treated by cutting surface fibers to a depth of 0.25-0.5 millimeter and the loose ends were brushed up with a wire brush to break up the surface filaments. Sample 7 was untreated and was used as a control.

The three samples were tested for liquid transport by placing each over a wire rack with one end in a one inch level of oil. A cotton chenille material of known weight was placed on TABLE 11 Weight of Oil Transferred From Reservoir To Cotton Chenille Time Sample 5 Sample 6 Sample 7 (minutes) (needle and (Control) tufted) brushed) 0 8.8 grams 8.8 grams 8.8 grams 18.1 grams 23.7 grams l6.5 grams 20 21.4 grams 26.4 grams 20.0 grams 30 22.2 grams 27.1 grams 2|.2 grams 40 23.2 grams 27.5 grams 22.9 grams From the data reported in Table II it can be seen that an increase in liquid transfer was obtained by needle tufting the wicking medium and that an additional and far greater increase in liquid transfer was achieved by cutting and raising surface fibers.

EXAMPLE 3 Six denier polypropylene tow of 250,000 total denier was needled with a 40 gauge, 9 barb needle using a five-sixteenths inch advance on a 96 needle per inch board. The needle penetration was five-sixteenths inch. Two passes were made, one on each side of the tow.

The resulting wick unit performed satisfactorily and in a manner similar to sample No. 1 of Example 1.

EXAMPLE 4 Six denier polyester tow was processed in the manner described in detail in Example 3.

The resulting wick unit, while performing satisfactorily, did not perform as well as the polypropylene of Example 3. This difference in performance is probably due somewhat to the less hydrophobic nature of the polyester fiber.

For particular purposes, e.g., for use as a railroad journal box lubricator, in addition to liquid transport and reservoir capacity it is necessary that the wicking unit maintain a constant pressure against the journal which is being lubricated. The function of maintaining contact with the journal can be fulfilled by a variety of devices. It is desirable, however, to provide controlled resiliency to maintain lubricant pressure and compensate for the vibratory oscillation of the journal. A mechanical spring system can be used to perform this function. Other pressure devices include elastomeric cellular structures and pressure pads of the type generally referred to as lofty nonwovens with randomized fiber orientation. A nonwoven pressure pad tested used 300 denier drawn nylon fibers bonded with an acrylonitrile binder to a weight of 27 ounces per square yard and a thickness of three-fourths inch.

Four or five such discs produced adequate pressure and resiliency. In use, the wicking unit can merely be wrapped around the pressure pad, preferably with its fibers aligned in the direction of the shaft surface motion.

It will be obvious to those skilled in the art that the nonwoven wick unit of the present invention will have numerous applications for the wicking of various liquids.

While the present invention has been described with reference to many particular details thereof it is not intended that these details shall act to limit the scope of this invention.

What is claimed is:

l. A nonwoven wick unit comprising a batt of filamentary tow having the majority of its filaments arranged in parallel and havin a plurality of the individual filaments of the tow restrained y needle punching to limit the distance between filaments without displacing more than 50 percent of the filaments from substantially their original alignment axis to selectively control liquid transport and reservoir capacity, said needle punched filaments having an average residual unbroken length of not less than about 4 inches.

2. The nonwoven wick unit of claim 1 wherein the individual filaments are from 3 denier to 6 denier and the unit contains between and 5,000 perforations per square inch.

3. The nonwoven wick unit of claim 2 wherein the filaments are man-made fibers.

4. The nonwoven wick unit of claim 3 wherein the filaments are viscose rayon fibers.

5. The nonwoven wick unit of claim 1 wherein a plurality of the s$rface fibers of the unit are broken and disoriented.

6. A railroad journal box lubricator comprising the combination of a nonwoven wick unit with a pressure producing means, said wick unit being a batt of filamentary tow having the majority of its filaments arranged in parallel and having a plurality of the individual filaments of the tow restrained to limit the distance between filaments without displacing more than 50 percent of the filaments from substantially their original alignment axis to selectively control liquid transport and reservoir capacity.

7. The railroad journal box lubricator of claim 6 wherein the filaments of said wick unit are restrained by needle punching the filamentary tow.

8. The railroad journal box lubricator of claim 7 wherein the individual filaments are from 3 denier to 6 denier and the unit contains between 125 and 5,000 perforations per square inch.

9. The railroad journal box lubricator of claim 8 wherein the filaments are man-made fibers.

10. The railroad journal box lubricator of claim 9 wherein the filaments are viscose rayon fibers.

11. The railroad journal box lubricator of claim 6 wherein a plurality of the surface fibers of the wick unit are broken and disoriented.

12. The railroad journal box lubricator of claim 6 wherein said pressure producing means is a spring.

13. The railroad journal box lubricator of claim 6 wherein said pressure producing means is an elastomeric cellular pressure pad.

14. The railroad journal box lubricator of claim 6 wherein said pressure producing means is a nonwoven pressure pad. 

1. A nonwoven wick unit comprising a batt of filamentary tow having the majority of its filaments arranged in parallel and having a plurality of the individual filaments of the tow restrained by needle punching to limit the distance between filaments without displacing more than 50 percent of the filaments from substantially their original alignment axis to selectively control liquid transport and reservoir capacity, said needle punched filaments having an average residual unbroken length of not less than about 4 inches.
 2. The nonwoven wick unit of claim 1 wherein the individual filaments are from 3 denier to 6 denier and the unit contains between 125 and 5,000 perforations per square inch.
 3. The nonwoven wick unit of claim 2 wherein the filaments are man-made fibers.
 4. The nonwoven wick unit of claim 3 wherein the filaments are viscose rayon fibers.
 5. The nonwoven wick unit of claim 1 wherein a plurality of the surface fibers of the unit are broken and disoriented.
 6. A railroad journal box lubricator comprising the combination of a nonwoven wick unit with a pressure producing means, said wick unit being a batt of filamentary tow having the majority of its filaments arranged in parallel and having a plurality of the individual filaments of the tow restrained to limit the distance between filaments without displacing more than 50 percent of the filaments from substantially their original alignment axis to selectively control liquid transport and reservoir capacity.
 7. The railroad journal box lubricator of claim 6 wherein the filaments of said wick unit are restrained by needle punching the filamentary tow.
 8. The railroad journal box lubricator of claim 7 wherein the individual filaments are from 3 denier to 6 denier and the unit contains between 125 and 5,000 perforations per square inch.
 9. The railroad journal box lubricator of claim 8 wherein the filaments are man-made fibers.
 10. The railroad journal box lubricator of claim 9 wherein the filaments are viscose rayon fibers.
 11. The railroad journal box lubricator of claim 6 wherein a plurality of the surface fibers of the wick unit are broken and disoriented.
 12. The rAilroad journal box lubricator of claim 6 wherein said pressure producing means is a spring.
 13. The railroad journal box lubricator of claim 6 wherein said pressure producing means is an elastomeric cellular pressure pad.
 14. The railroad journal box lubricator of claim 6 wherein said pressure producing means is a nonwoven pressure pad. 